Transfer substrate and method for fabricating organic electroluminescent element

ABSTRACT

A transfer substrate includes a light transmissive support substrate; a light-heat conversion layer formed on the light transmissive support substrate; and a transfer layer formed on the light heat conversion layer. The transfer layer is a layer transferred as a luminescent layer of an organic electroluminescent element and is made of a metal complex, a fluorescent luminescent dopant and an aromatic hydrocarbon whose matrix skeleton has four to seven rings.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/190,740, filed on Aug. 13, 2008 the entirety of which areincorporated herein by reference to the extent permitted by law. Thepresent application claims priority to Japanese Patent Application No.JP2007-212025 filed in the Japan Patent Office on Aug. 16, 2007, theentire contents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transfer substrate and a method forfabricating an organic electroluminescent element. More particularly,the present invention relates to a transfer substrate adapted for use inpattern formation of a luminescent layer and also to a method forfabricating an organic electroluminescent element using the transfersubstrate.

2. Description of the Related Art

In recent years, attention has been drawn to display devices usingorganic electroluminescent elements (so-called organic EL element) as aflat panel display device that is lightweight and high in efficiency.

The organic electroluminescent element used for such a display device isprovided on a transparent substrate such as, for example, glass and isso arranged that an anode made of ITO (indium tin oxide: transparentelectrode), an organic layer and a cathode are laminated in this orderas viewed from the substrate side. The organic layer has such anarrangement that a hole injection layer, a hole transport layer and anelectron transportable luminescent layer are successively laminated asviewed from the anode side. With the organic electroluminescent elementthus arranged, the electrons injected from the cathode and the holesinjected from the anode are re-combined at the luminescent layer,whereupon light is taken out from the substrate side through the anode.

A full-color display device using such organic electroluminescentelements is formed such that organic electroluminescent elements ofindividual colors including R (red), G (green) and B (blue) are arrayedon a substrate. In the manufacture of such a display device, luminescentlayers made of organic light-emitting materials capable of emitting therespective colors should be formed in pattern for every luminescentelement. The pattern formation of the luminescent layers is now carriedout, for example, according to a shadow masking process wherein aluminescent material is vacuum deposited or coated through a mask formedwith an opening pattern in a sheet or by an ink jet technique.

In the pattern formation made by the shadow masking process, adifficulty has been involved in further miniaturization and a highdegree of integration of organic electroluminescent elements because ofa difficulty in further microfabrication of an opening pattern formed inthe mask and also of a difficulty in pattern formation of highpositional accuracy in a luminescent element region owing to theflexibility and elongation of the mask. Upon contact of the mask formedwith an opening pattern therein, functional layers including apreviously formed organic layer are liable to break, thereby causing aproduction yield to be lowered.

The pattern formation by the ink jet process is limited in patterningaccuracy, for which a difficulty is involved in microfabrication and ahigh degree of integration of luminescent elements and also in theformation of a large-sized substrate.

To avoid this, there has been proposed a transfer process (i.e. a heator thermal transfer process) using an energy source (heat source) as anew pattern forming process of a luminescent layer constituted of anorganic material and other functional layers. The display device usingthe thermal transfer process is manufactured, for example, in thefollowing way. Initially, a lower electrode is formed on a substrate ofa display device (hereinafter referred to as “device substrate”). On theother hand, a luminescent layer is formed on another substrate(hereinafter referred to “transfer substrate”) through a light-heatconversion layer. The device substrate and the transfer substrate arearranged so that the luminescent layer and the lower electrode arefacing each other, under which a laser beam is irradiated from thetransfer substrate side thereby causing the luminescent layer to bethermally transferred onto the lower electrode of the device substrate.At this stage, when the spot irradiated laser beam is scanned, theluminescent layer is thermally transferred only at a given region on thelower electrode in high positional accuracy (see Japanese PatentLaid-open Nos. 2002-110350 and Hei 11-260549).

With respect to an organic electroluminescent element fabricatedaccording to the thermal transfer process, there has been proposed amethod of improving a luminescent efficiency and a luminance half-timelife by subjecting a device substrate and a transfer substrate to heattreatment prior to heat or thermal transfer of a luminescent layer (seeJapanese Patent Laid-open No. 2003-229259).

Further, there has been proposed a method of increasing sensitivitywherein a sublimating compound is used as a donor of high sensitivity ofa laser-induction thermal image-forming system (see Japanese PatentLaid-open No. Hei 10-6643).

On the other hand, there has been disclosed a technique wherein acompound having an aromatic ring having four or more condensedpolycyclic hydrocarbons is used as a dopant in a luminescent layer of anorganic electroluminescent element (see Japanese Patent Laid-open No.Hei 9-241629).

However, the luminescent elements obtained by use of such thermaltransfer processes have problems in that the transfer layer degrades bylaser irradiation although depending on the types of organic materialsused for the transfer layer, so that when compared with a luminescentelement made by the shadow mask process, the luminescent efficiencybecomes lower, the drive voltage increases, and the luminance half-timelife becomes shorter. Thus, the improvements made by such techniques asset out above are not satisfactory with respect to the effects broughtabout thereby.

SUMMARY OF THE INVENTION

It is desirable to provide a transfer substrate used for the manufactureof an organic electroluminescent element that is able to keep a highluminescent efficiency and luminance half-time life.

It is also desirable to provide a method for fabricating an organicelectroluminescent element that makes use of such a transfer substrateas mentioned above and is able to improve a luminescent efficiency and aluminance half-time life.

In order to achieve the above desire, an embodiment of the presentinvention provides a transfer substrate including a light transmissivesupport substrate, a light-heat conversion layer formed on the supportsubstrate, and a transfer layer formed on the light-heat conversionlayer wherein the transfer layer is a layer to be transferred as aluminescent layer of the organic electroluminescent element and is madeof a mixture of a metal complex, a fluorescent luminescent dopant and anaromatic hydrocarbon whose matrix skeleton has four to seven rings, oris tetracyclic to heptacyclic.

Further, another embodiment of the present invention provides a methodfor fabricating an organic electroluminescent element using such atransfer substrate as mentioned above, which is characterized in that aluminescent layer is formed by use of the transfer substrate. In thiscase, a transfer substrate is placed in face-to-face relation with adevice substrate under conditions where the transfer layer is directedtoward the device substrate side. The transfer layer is sublimated bybeam irradiation from the support substrate side to transfer thetransfer layer above the device substrate thereby forming a luminescentlayer.

In such an arrangement as set out above, since the transfer layer of thetransfer substrate is made of a ternary material of a metal complex, afluorescent luminescent dopant and an aromatic hydrocarbon whose matrixskeleton has four to seven rings, the resulting luminescent layer formedby sublimation of the transfer layer is constituted of the ternarymaterial. It has been confirmed that although the aromatic hydrocarbondoes not contribute to luminescence in the luminescent layer made up ofsuch a ternary material, a higher luminescent efficiency and a longerluminance half-time life are achieved over the case containing noaromatic hydrocarbon. Moreover, such a luminescent layer is higher inuniformity of mixing state of the three types of material and has moreaccurately controlled material ratios than that obtained by a vacuumco-deposition process.

Hence, according to the embodiments of the present invention, there canbe obtained a luminescent layer made of a ternary material, whichensures a high luminescent efficiency and an improved luminancehalf-time life, in high uniformity and at material ratios of highaccuracy. Using this luminescent layer, there can be obtained an organicelectroluminescent element which is further improved in luminescentefficiency and luminance half-time life.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing a transfer substrateaccording to an embodiment of the present invention;

FIGS. 2A and 2B are schematic sectional views showing a step of afabricating method of a display device including a method for making anorganic electroluminescent element using the transfer substrateaccording to the embodiment;

FIGS. 3A and 3B are schematic sectional views showing a step subsequentto the step of FIG. 2B;

FIGS. 4A and 4B are schematic sectional views showing a step subsequentto the step of FIG. 3B;

FIG. 5 is a schematic sectional view showing another type of displaydevice obtained by a fabricating method according to another embodimentof the present invention;

FIGS. 6A and 6B are circuit diagrams of the display device according tofurther embodiment of the present invention;

FIG. 7 is a schematic view showing a module-shaped display device of asealed type to which the present invention is applied;

FIG. 8 is a perspective view showing a television set to which thepresent invention is applied;

FIGS. 9A and 9B are schematic views showing a digital camera to whichthe present invention is applied, wherein FIG. 9A is a perspective viewof the camera as viewed from a front side and FIG. 9B is a perspectiveview of the camera as viewed from a back side;

FIG. 10 is a perspective view showing a note-type personal computer, towhich the present invention is applied;

FIG. 11 is a perspective view showing a video camera, to which thepresent invention is applied; and

FIGS. 12A to 12G are schematic views showing a mobile device, to whichthe present invention is applied, wherein FIG. 12A is a plan view of thedevice in an opened state, FIG. 12B is a side view, FIG. 12C is a planview of the device in a closed state, FIG. 12D is a left side view, FIG.12E is a right side view, FIG. 12F is a top view, and FIG. 12G is abottom view.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention are now described with reference to theaccompanying drawings. In the following embodiments, there areillustrated a transfer substrate used in the case where a full-colordisplay device is fabricated wherein organic electroluminescent elementsof the respective colors including red (R), green (G) and blue (B) arearrayed on a substrate, and also a method for fabricating a displaydevice using the transfer substrate.

<Transfer Substrate>

FIG. 1 is a sectional view illustrating an arrangement of a transfersubstrate 1 according to an embodiment of the invention. The transfersubstrate 1 of this figure is one, with which a luminescent layer of anorganic electroluminescent element is formed, and includes a supportsubstrate 11, on which a light-heat conversion layer 13, an oxidationprotective film 15, if necessary, and a transfer layer 17 are formed inthis order.

The support substrate 11 is made of a material capable of beingtransmitting with light hν of a given wavelength that is irradiated inthe course of transfer by use of this transfer substrate 1. Forinstance, where a laser beam with a wavelength of about 800 nm from asolid laser light source is used as this light hν, a glass substrate maybe used as the support substrate 11.

The light-heat conversion layer 13 is made of a material that has a highlight-heat conversion efficiency of converting the light hν to heat anda high melting point. For instance, where the afore-indicated laser beamwith a wavelength of about 800 nm is used as the light hν, thelight-heat conversion layer 12 is preferably made of a high meltingmetal with a low reflectance such as chromium (Cr), molybdenum (Mo) orthe like although not limited thereto. This light-heat conversion layer12 should be so controlled in thickness as to obtain a necessary andsufficient light-heat conversion efficiency. For example, where thelight-heat conversion layer 12 is constituted of a molybdenum (Mo) film,a film thickness of about 200 nm is used. The light-heat conversionlayer 13 is formed herein, for example, by a sputtering method whereinMo is formed in a thickness of 200 nm.

The oxidation protective layer 15 is made of silicon nitride (SiN_(x))or silicon oxide (SiO₂). The oxidation protective layer 15 made of thejust-mentioned material is formed, for example, by a CVD (chemical vapordeposition) process.

The transfer layer 17 is constituted of a) a metal complex, b) afluorescent luminescent dopant, and c) an aromatic hydrocarbon whosematrix skeleton has four to seven rings. These materials are describedin more detail hereinafter.

The three types of these materials may be all mixed together and formedas a single layered structure for use as the transfer layer 17, or maybe formed as a double-layered structure including a mixed layer of a)metal complex+b) fluorescent luminescent dopant, and a layer of c)aromatic hydrocarbon. Alternatively, a three-layered structure whereinthe respective materials are formed as a single layer may be used.

It will be noted that the ratio of c) aromatic hydrocarbon to the totalof the three materials in the transfer layer 17 is not larger than 50 wt%.

The transfer layer 17 may contain, aside from the three types ofmaterials, solvents used for the formation of the transfer layer 17.

Next, a) metal complex, b) fluorescent luminescent dopant and c)aromatic hydrocarbon are now described in detail.

a) Metal Complex

a) Meal complex is preferably a quinolilato complex of the Group XIIImetal of the Periodic Table. More particularly, quinolilato complexeswherein quinolinol is coordinated to a metal selected from aluminium,gallium and indium, or aluminium complexes are preferred. It will benoted that aluminium complexes may be those disclosed in Japanese PatentLaid-open Nos. Sho 63-264692, Hei 3-255190, Hei 5-70733, Hei 5-258859,Hei 6-215874 and the like.

Specific examples of such a) metal complex includetris(8-quinolinolato)aluminium, bis(2-methyl-8-quinolinolato)aluminiumoxide, tris(8-quinolinolato)indium, tris(5-methyl-8-quinolinolato)aluminium, tris(5-chloro-8-quinolinolato)gallium,5,7-dichloro-8-quinolinoloato aluminium,tris(5,7-dibromo-8-quinolinolato)aluminium, and the like.

Aside from 8-quinolinol or derivatives thereof, aluminium complexeshaving other types of ligands may be used and includebis(2-methyl-8-quinolinolato)(phenolato)aluminium (III),bis(2-methyl-8-quinolinolato)(ortho-cresolato)aluminium (III),bis(2-methyl-8-quinolinolato)(meta-cresolato)aluminium (III),bis(2-methyl-8-quinolinolato)(para-cresolato)aluminium (III),bis(2-methyl-8-quinolinolato)(ortho-phenylphenolato)aluminium (III),bis(2-methyl-8-quinolinolato)(meta-phenylphenolato)aluminium (III),bis(2-methyl-8-quinolinolato)(para-phenylphenolato)aluminium (III),bis(2-methyl-8-quinolinolato)(2,3-dimethylphenolato)aluminium (III),bis(2-methyl-8-quinolinolato)(2,6-dimethylphenolato)aluminium (III),bis(2-methyl-8-quinolinolato)(3,4-dimethylphenolato)aluminium (III),bis(2-methyl-8-quinolinolato)(3,5-dimethylphenolato)aluminium (III),bis(2-methyl-8-quinolinolato)(3,5-di-tert-butylphenolato)aluminium(III), bis(2-methyl-8-quinolinolato)(2,6-diphenylphenolato)aluminium(III), bis(2-methyl-8-quinolinolato)(2,4,6-triphenylphenolato)aluminium(III), bis(2-methyl-8-quinolinolato)(2,3,6-trimethylphenolato)aluminium(III),bis(2-methyl-8-quinolinolato)(2,3,5,6-tetramethylphenolato)aluminium(III), bis(2-methyl-8-quinolinolato)(1-naphtholato)aluminium (III),bis(2-methyl-8-quinolinolato)(2-naphtholato)aluminium (III),bis(2,4-dimethyl-quinolinolato)(ortho-phenylphenolato)aluminium (III),bis(2,4-dimethyl-8-quinolinolato)(para-phenylphenolato)aluminium (III),bis(2,4-dimethyl-8-quinolinolato)(meta-phenylphenolato)aluminium (III),bis(2,4-dimethyl-8-quinolinolato)(3,5-dimethylphenolato)aluminium (III),bis(2,4-dimethyl-8-quinolinolato)(3,5-di-tert-butylphenolato)aluminium(III), bis(2-methyl-4-ethyl-8-quinolinolato)(para-cresolato)aluminium(III),bis(2-methyl-4-methoxy-8-quinolinolato)(para-phenylphenolato)aluminium(III), bis(2-methyl-5-cyano-8-quinolinolato)(ortho-cresolato)aluminium(III),bis(2-methyl-6-trifluoromethyl-8-quinolinolato)(2-naphtholato)aluminium(III), and the like.

Besides, there may be mentioned bis(2-methyl-8-quinolinolato)aluminium(III)-μ-oxo-bis(2-methyl-8-quinolinolato)aluminium (III),bis(2,4-dimethyl-8-quinolinolato)aluminium(III)-μ-oxo-bis(2,4-dimethyl-8-quinolinolato)aluminium (III),bis(4-ethyl-2-methyl-8-quinolinolato)aluminium(III)-μ-oxo-bis(4-ethyl-2-methyl-8-quinolinolato)aluminium (III),bis(2-methyl-4-methoxyquinolinolato)aluminium(III)-μ-oxo-bis(2-methyl-4-methoxyquinolinolato)aluminium (III),bis(5-cyano-2-methyl-8-quinolinolato)aluminium(III)-μ-oxo-bis(5-cyano-2-methyl-8-quinolinolato)aluminium (III),bis(2-methyl-5-trifluoromethyl-8-quinolinolato)aluminium(III)-β-oxo-bis(2-methyl-5-trifluoromethyl-8-quinolinolato)aluminium(III), and the like.

b) Fluorescent Luminescent Dopant

As b) fluorescent luminescent dopant, an organic material capable ofenergy transfer with a) metal complex is preferred and shouldparticularly be a green luminescent material or a red luminescentmaterial. In this connection, a transfer substrate 1 provided thereonwith a transfer layer 17 g containing a green luminescent material isused as a transfer substrate 1 g for forming a green luminescent layer.Likewise, a transfer substrate 1 provided with a transfer layer 17 rcontaining a red luminescent material is used as a transfer substrate 1r for forming a red luminescent layer.

As a green luminescent material, there are used compounds having aluminescence peak within a wavelength range of about 490 nm to 580 nm.Such compounds are organic materials including naphthalene derivatives,anthracene derivatives, pyrene derivatives, naphthacene derivatives,fluoranthene derivatives, perylene derivatives, coumarin derivatives,quinacridone derivatives, indino[1,2,3-cd]perylene derivatives,bis(azinyl)methene boron complexes, pyrane dyestuffs and the like. Ofthese, preferred ones are selected from aminoanthracene derivatives,fluoranthene derivatives, coumarin derivatives, quinacridonederivatives, indino[1,2,3-cd]perylene derivatives, andbis(azinyl)methene boron complexes.

The red luminescent materials used include those illustrated below andincluding perylene derivatives of the general formula (1),diketopyrolo-pyrole derivatives of the general formula (2), pyromethenecomplexes of the general formula (3), pyrane derivatives of the generalformula (4) or styryl derivatives of the general formula (5). The redluminescent materials are now described in more detail.

—Perylene Derivatives—

As a red luminescent material, there is used, for example, a compound ofthe following general formula (1) (diindino[1,2,3-cd]perylenederivative).

In the general formula (1), X¹ to X²⁰ independently represent hydrogen,a halogen, a hydroxyl group, a substituted or unsubstituted carbonylgroup having not larger than 20 carbon atoms, a substituted orunsubstituted carbonyl ester group having not larger than 20 carbonatoms, a substituted or unsubstituted alkyl group having not larger than20 carbon atoms, a substituted or unsubstituted alkenyl group having notlarger than 20 carbon atoms, a substituted or unsubstituted alkoxylgroup having not larger than 20 carbon atoms, a cyano group, a nitrogroup, a substituted or unsubstituted silyl group having not larger than30 carbon atoms, a substituted or unsubstituted aryl group having notlarger than 30 carbon atoms, a substituted or unsubstituted heterocyclicgroup having not larger than 30 carbon atoms, or a substituted orunsubstituted amino group having not larger than 30 carbon atoms.

The aryl group represented by X¹ to X²⁰ in the general formula (1)includes, for example, a phenyl group, a 1-naphthyl group, a 2-naphthylgroup, a flluorenyl group, a 1-anthryl group, a 2-anthryl group, a9-anthryl group, a 1-phenanthryl group, a 2-phenanthryl group, a3-phenanthryl group, a 4-phenanthryl group, a 9-phenanthryl group, a1-naphthacenyl group, a 2-naphthacenyl group, a 9-naphthacenyl group, a1-pyrenyl group, a 2-pyrenyl group, a 4-pyrenyl group, a 1-chrysenylgroup, a 6-chrysenyl group, a 2-fluoranthenyl group, a 3-fluoranthenylgroup, a 2-biphenylyl group, a 3-biphenylyl group, a 4-biphenylyl group,an o-tolyl group, a m-tolyl group, a p-tolyl group, a p-t-butylphenylgroup or the like.

The heterocyclic group represented by X¹ to X²⁰ includes a five-memberedor six-membered aromatic heterocyclic group containing O, N or S as aheteroatom and a condensed polycyclic aromatic heterocyclic group having2 to 20 carbon atoms. These aromatic heterocyclic groups and condensedpolycyclic aromatic heterocyclic group include a thienyl group, a furylgroup, a pyrolyl group, a pyridyl group, a quinolyl group, a quinoxalylgroup, an imidazopyridyl group, a benzothiazole group and the like.Typical examples include a 1-pyrolyl group, a 2-pyrolyl group, a3-pyrolyl group, a pyradinyl group, a 2-pyridinyl group, a 3-pyridinylgroup, a 4-pyridinyl group, a 1-indolyl group, a 2-indolyl group, a3-indolyl group, a 4-indolyl group, a 5-indolyl group, a 6-indolylgroup, a 7-indolyl group, a 1-isoindolyl group, a 2-isoindolyl group, a3-isoindolyl group, a 4-isoindolyl group, a 5-isoindolyl group, a6-isoindolyl group, a 7-isoindolyl group, a 2-furyl group, a 3-furylgroup, a 2-benzofuranyl group, a 3-benzofuranyl group, a 4-benzofuranylgroup, a 5-benzofuranyl group, a 6-benzofuranyl group, a 7-benzofuranylgroup, a 1-isobenzofuranyl group, a 3-isobenzofuranyl group, a4-isobenzofuranyl group, a 5-isobenzofuranyl group, a 6-isobenzofuranylgroup, a 7-isobenzofuranyl group, a quinolyl group, a 3-quinolyl group,a 4-quinolyl group, a 5-quinolyl group, a 6-quinolyl group, a 7-quinolylgroup, a 8-quinolyl group, a 1-isoquinolyl group, a 3-isoquinolyl group,a 4-isoquinolyl group, a 5-isoquinolyl group, a 6-isoquinolyl group, a7-isoquinolyl group, a 8-isoquinolyl group, a 2-quinoxalinyl group, a5-quinoxalinyl group, a 6-quinoxalinyl group, a 1-carbazolyl group, a2-carbazolyl group, a 3-carbazolyl group, a 4-carbazolyl group, a9-carbazolyl group, a 1-phenanthridinyl group, a 2-phenanthridinylgroup, a 3-phenanthridinyl group, a 4-phenanthridinyl group, a6-phenanthridinyl group, a 7-phenanthridinyl group, a 8-phenanthridinylgroup, a 9-phenanthridinyl group, a 10-phenanthridinyl group, a1-acrydinyl group, a 2-acrydinyl group, a 3-acrydinyl group, a4-acrydinyl group, a 9-acrydinyl group and the like.

The amino group represented by X¹ to X²⁰ may be either of an alkylaminogroup, an arylamino group, an aralkylamino group or the like. Thesepreferably have an aliphatic group having 1 to 6 carbon atoms in totaland/or a 1monocyclic to tetracyclic aromatic hydrocarbon ring. Suchgroups include a dimethylamino group, a diethylamino group, adibutylamino group, a diphenylamino group, a ditolylamino group, abisbiphenylamino group and a dinaphthylamino group.

Two or more of the above substituent groups may form a condensed ringand may have a further substituent.

Specific examples of the diindino[1,2,3-cd]perylene derivative suitablyemployed as a red luminescent material of the transfer layer 17 includethose of the following compounds (1)-1 to (1)-8 although not limited tothose compounds in the practice of the invention.

—Diketopyrolopyrole Derivatives—

A compound of the following general formula (2) (i.e. adiketopyrolopyrole derivative) is used, for example, as a redluminescent material of the transfer layer 17

wherein Y¹ and Y² independently represent an oxygen atom or asubstituted or unsubstituted imino group, Y³ to Y⁸ independentlyrepresent hydrogen, a halogen, a substituted or unsubstituted alkylgroup having not larger than 20 carbon atoms, a substituted orunsubstituted alkenyl group having not larger than 20 carbon atoms, asubstituted or unsubstituted aryl group having not larger than 30 carbonatoms, a substituted or unsubstituted heterocyclic group having notlarger than 30 carbon atoms, or a substituted or unsubstituted aminogroup having not larger than 30 carbon atoms, and Ar¹ and Ar² eachrepresents a divalent group selected from a substituted or unsubstitutedaromatic hydrocarbon group and a substituted or unsubstituted aromaticheterocyclic group.

In the general formula (2), the substituted or unsubstituted aryl grouprepresented by Y³ to Y⁸, the heterocyclic group represented by Y³ to Y⁸,and the amino group represented by Y³ to Y⁸ are, respectively, same asthose indicated with respect to the perylene derivative of the generalformula (1). Two or more of the substituted groups may form a condensedring and may further have a substituent group as in the foregoing case.

Specific example of the diketopyrolopyrole derivative suited as a redluminescent material of the transfer layer 17 include those indicated ascompounds (2)-1 to (2)-14 although not limited thereto in the practiceof the invention.

—Pyromethene Complexes—

As a red luminescent material of the transfer layer 17, there is used,for example, a compound (pyromethene complex) of the following generalformula (3)

wherein Z¹ to Z⁹ independently represent hydrogen, a halogen, asubstituted or unsubstituted alkyl group having not larger than 20carbon atoms, a substituted or unsubstituted alkenyl group having notlarger than 20 carbon atoms, a substituted or unsubstituted alkoxylgroup having not larger than 20 carbon atoms, a cyano group, a nitrogroup, a substituted or unsubstituted silyl group having not larger than30 carbon atoms, a substituted or unsubstituted aryl group having notlarger than 30 carbon atoms, a substituted or unsubstituted heterocyclicgroup having not larger than 30 carbon atoms, or a substituted orunsubstituted amino group having not larger than 30 carbon atoms.

In the general formula (3), the substituted or unsubstituted aryl grouprepresented by Z¹ to Z⁹, the heterocyclic group represented by Z¹ to Z⁹,and the amino group represented by Z¹ to Z⁹ are, respectively, same asthose indicated with respect to the perylene derivative of the generalformula (1). Two or more of the substituted groups may form a condensedring and may further have a substituent group as in the foregoing case.

Specific examples of the pyromethene complex suited as a red luminescentmaterial of the transfer layer 17 include the following compounds (3)-1to (3)-33 although not limited to those compounds in the presentinvention.

—Pyrane Derivatives—

The compound (pyrane derivative) represented, for example, by thefollowing general formula (4) is used as a red luminescent material ofthe transfer layer 17

wherein L¹ to L⁶ independently represent hydrogen, a substituted orunsubstituted alkyl group having not larger than 20 carbon atoms, asubstituted or unsubstituted alkenyl group having not larger than 20carbon atoms, a substituted or unsubstituted alkoxyl group having notlarger than 20 carbon atoms, a cyano group, a nitro group, a substitutedor unsubstituted silyl group having not larger than 30 carbon atoms, asubstituted or unsubstituted aryl group having not larger than 30 carbonatoms, a substituted or unsubstituted heterocyclic group having notlarger than 30 carbon atoms, or a substituted or unsubstituted aminogroup having not larger than 30 carbon atoms, and L¹ and L⁴ or L² and L³may take a cyclic structure through a hydrocarbon.

In the general formula (4), the substituted or unsubstituted aryl grouprepresented by L¹ to L⁶, the substituted or unsubstituted heterocyclicgroup represented by L¹ to L⁶, and the substituted or unsubstitutedamino group represented by L¹ to L⁶ are, respectively, similar to thosegroups represented with respect to the perylene derivatives of thegeneral formula (1). Although L¹ and L⁴ or L² and L³ may take a cyclicstructure through a hydrocarbon, two or more of the above substituentsmay form a condensed ring and may further have a substituent group.

Specific examples of pyrane derivative suited as a red luminescentmaterial of the transfer layer 17 include the following compounds (4)-1to (4)-7 although not limited thereto.

—Styryl Derivatives—

The compound represented, for example, by the following general formula(5) is used as a red luminescent material of the transfer layer 17

wherein T¹ to T³ independently represent a substituted or unsubstitutedaryl group having not larger than 30 carbon atoms, or a substituted orunsubstituted heterocyclic group having not larger than 30 carbon atoms,and T⁴ represents a substituted or unsubstituted phenylene moiety thatmay have a cyclic structure.

In the general formula (5), the substituted or unsubstituted aryl grouprepresented by T¹ to T³ and the substituted or unsubstitutedheterocyclic group represented by T¹ to T³ are, respectively, similar tothose groups represented with respect to the perylene derivative of thegeneral formula (1).

Two or more of the above substituent groups may form a condensed ringand may further have a substituent group. In this connection, the groupsubstituted to T¹ to T⁴ includes, for example, hydrogen, a halogen, ahydroxyl group, a substituted or unsubstituted carbonyl group having notlarger than 20 carbon atoms, a substituted or unsubstituted carbonylester group having not larger than 20 carbon atoms, a substituted orunsubstituted alkyl group having not larger than 20 carbon atoms, asubstituted or unsubstituted alkenyl group having not larger than 20carbon atoms, a substituted or unsubstituted alkoxyl group having notlarger than 20 carbon atoms, a cyano group, a nitro group, an aminogroup or the like. Besides, the amino group may be any of an alkylaminogroup, an arylamino group, an aralkyl group or the like. Thesepreferably have an aliphatic group having 1 to 6 carbon atoms in totaland/or a moncyclic to tetracyclic aromatic hydrocarbon. Such groupsinclude a dimethylamino group, a diethylamino group, a dibutylaminogroup, a diphenylamino group, a ditolylamino group, a bisbiphenylylaminogroup, a dinaphthylamino group and the like.

Specific examples of the styryl derivative suitably used as a redluminescent material of the transfer layer 17 include the followingcompounds (5)-1 to 5-(35) although not limited to these in the practiceof the invention.

The perylene derivative of the general formula (1), thediketopyrolopyrole derivative of the general formula (2), thepyromethene complex of the general formula (3), the pyrane derivative ofthe general formula (4) or the styryl derivative of the general formula(5), which is used as a red luminescent material of the transfer layer17 as set out hereinabove, should preferably have a molecular weight ofnot greater than 2000, more preferably not greater than 1500 and mostpreferably not greater than 1000. The reason for this is that it isconsidered that if the molecular weight is great, there is concern thatdepositability becomes worsened in case where an element is made byvacuum deposition.

c) Aromatic Hydrocarbons

Specific examples of aromatic hydrocarbons whose matrix skeleton hasfour to seven rings include pyrene, triphenylene, fluoranthene, crycene,naphthacene, pentacene, perylene or coronene as a skeleton thereof.Besides, the following compounds wherein a benzene ring is added to maybe mentioned, for example.

That is, mention is made of benzo[b]fluorene, benzo[c]phenanthrene,benzo[ghi]fluoranthene, benzo[a]anthracene, benzo[a]pyrene,benzo[e]pyrene, benzo[j]fluoranthene, benzo[a]naphthacene,benzo[b]crycene, benzo[c]crycene, benzo[ghi]perylene,dibenzo[a,c]anthracene, dibenzo[a,h]anthracene, dibenzo[a,j]anthracene,naphtho[a]anthracene, dibenzo[b,def]crycene, dibenzo[b,k]perylene,dibenzo[cd, lm]perylene, dibenzo[g,p]crycene, naphtho[bcd]perylene,phenanthro[3,4-c]phenanthrene, benzo[a]coronene,benzo[ghi]naphtho[cde]perylene, dibenzo[bc,ef]coronene,dinaphtho[defg,opqr]pentacene, naphtho[g]coronene,benzo[rst]dinaphtho[defg,ijkl]pentaphene,benzo[rst]phenanthro[1,10,9-cde]pentaphene,dibenzo[j,lm]naphtho[ab]perylene, tetrabenzo[a,cd,f,lm]perylene,pentabenzo[a,cd,f,j,lm]perylene and the like.

Further, these matrix skeletons may have a substituent group and mayhave hydrogen, a halogen, a hydroxyl group, a substituted orunsubstituted carbonyl group having not larger than 20 carbon atoms, asubstituted or unsubstituted carbonyl ester group having not larger than20 carbon atoms, a substituted or unsubstituted alkyl group having notlager than 20 carbon atoms, a substituted or unsubstituted alkenyl grouphaving not larger than 20 carbon atoms, a substituted or unsubstitutedalkoxyl group having not larger than 20 carbon atoms, a cyano group, anitro group, a substituted or unsubstituted silyl group having notlarger than 30 carbon atoms, a substituted or unsubstituted aryl grouphaving not larger than 30 carbon atoms, a substituted or unsubstitutedheterocyclic group having not larger than 30 carbon atoms, or asubstituted or unsubstituted amino group having not larger than 30carbon atoms.

The aryl group used as a substituent group bonded to the matrix skeletonincludes, for example, a phenyl group, a 1-naphthyl group, a 2-naphthylgroup, a fluorenyl group, a 1-anthryl group, a 2-anthryl group, a9-anthryl group, a 1-phenathryl group, a 2-phenathryl group, a3-phenathryl group, a 4-phenathryl group, a 9-phenathryl group, a1-naphthacenyl group, a 2-naphthacenyl group, a 9-naphthacenyl group, a1-pyrenyl group, a 2-pyrenyl group, a 4-pyrenyl group, a 1-crycenylgroup, a 6-crycenyl group, a 2-fluoranthenyl group, a 3-fluoranthenylgroup, a 2-biphenylyl group, a 3-biphenylyl group, a 4-biphenylyl group,an o-tolyl group, a m-tolyl group, a p-tolyl group, a p-t-butylphenylgroup or the like.

The heterocyclic group used as the substituent group bonded to thematrix skeleton includes a five or six-membered aromatic heterocyclicgroup containing O, N or S as a heteroatom or a condensed polycyclicaromatic heterocyclic group having 2 to 20 carbon atoms.

Examples of the aromatic heterocyclic group and condensed polycyclicaromatic heterocyclic group include a thienyl group, a furyl group apyrolyl group, a pyridyl group, a quinolyl group, a quinoxalyl group, animidazopyridyl group, and a benzothiazole group. Typical examplesinclude a 1-pyrolyl group, a 2-pyrolyl group, a 3-pyrolyl group, apyradinyl group, a 2-pyridinyl group, a 3-pyridinyl group, a 4-pyridinylgroup, a 1-indolyl group, a 2-indolyl group, a 3-indolyl group, a4-indolyl group, a 5-indolyl group, a 6-indolyl group, a 7-indolylgroup, a 1-isoindolyl group, a 2-isoindolyl group, a 3-isoindolyl group,a 4-isoindolyl group, a 5-isoindolyl group, a 6-isoindolyl group, a7-isoindolyl group, a 2-furyl group, a 3-furyl group, a 2-benzofuranylgroup, a 3-benzofuranyl group, a 4-benzofuranyl group, a 5-benzofuranylgroup, a 6-benzofuranyl group, a 7-benzofuranyl group, a1-isobenzofuranyl group, a 3-isobenzofuranyl group, a 4-isobenzofuranylgroup, a 5-isobenzofuranyl group, a 6-isobenzofuranyl group, a7-isobenzofuranyl group, a quinolyl group, a 3-quinolyl group, a4-quinolyl group, a 5-quinolyl group, a 6-quinolyl group, a 7-quinolylgroup, a 8-quinolyl group, a 1-isoquinolyl group, a 3-isoquinolyl group,a 4-isoquinolyl group, a 5-isoquinolyl group, a 6-isoquinolyl group, a7-isoquinolyl group, a 8-isoquinolyl group, a 2-quinoxalynyl group, a5-quinoxalynyl group, a 6-quinoxalynyl group, a 1-carbazolyl group, a2-carbazolyl group, a 3-carbazolyl group, a 4-carbazolyl group, a9-carbazolyl group, a 1-phenanthridinyl group, a 2-phenanthridinylgroup, a 3-phenanthridinyl group, a 4-phenanthridinyl group, a6-phenanthridinyl group, a 7-phenanthridinyl group, a 8-phenanthridinylgroup, a 9-phenanthridinyl group, a 10-phenanthridinyl group, a1-acrydinyl group, a 2-acrydinyl group, a 3-acrydinyl group, a4-acrydinyl group, a 9-acrydinyl group, and the like.

In order to make the transfer layer 17 constituted of a) metal complex,b) fluorescent luminescent dopant and c) aromatic hydrocarbon as statedhereinabove, there may be used, aside from a dry process such as avacuum deposition process, a wet process including a coating processsuch as a spin coating process, a dipping process, a doctor bladeprocess, a jet coating process, a spray coating process or the like, ora printing process such as an ink jet process, an offset process, aletterpress process, an intaglio printing process, a screen printingprocess, a microgravure coating process or the like. Moreover, the dryand wet processes may be used in combination although depending on theproperties of the respective materials used as a) metal complex, b)fluorescent luminescent dopant and c) aromatic hydrocarbon.

In the wet process, it is necessary to select a solvent depending on theproperties or natures of the respective organic layers and therespective members. Specific examples of the solvent include, forexample, ether solvents (monovalent alcohols) such as ethylene glycolmonomethyl ether, ethylene glycol monoethyl ether, propylene glycolmonomethyl ether and the like, glycols (divalent alcohols) such asethylene glycol, diethylene glycol, propylene glycol and the like,polyols such as 1,2-hexanediol, 2,4,6-hexanetriol and the like, ketonesolvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone,cyclohexanone, 4-methoxy-4-methylpentanone and the like, hydrocarbonsuch as hexane, decane, cyclohexane, decalin and the like, estersolvents such as ethyl acetate, n-propyl acetate and the like, aproticpolar solvents such as N,N-dimethylformamide (DMF), dimethylsulfoxide(DMSO), N-methylpyrrolidone, y-butyl lactone,1,3-dimethyl-2-imidazolidinone, acetonitrile, tetrahydrofuran and thelike, aromatic solvents such as benzene, toluene, xylene, mesitylene,chlorobenzene, tetralin and the like, and halomethane solvents such aschloroform, dichloromethane, dichloroethane and the like.

These solvent may be used singly or in combination of two or more.

<Method for Fabricating a Display Device>

FIGS. 2A to FIG. 4B are, respectively, a sectional view showing the stepof a method of fabricating a display device including a method ofmanufacturing an organic electroluminescent element using such atransfer substrate 1 as set out hereinbefore. The fabrication procedureis illustrated with reference to these figures.

Initially, as shown in FIG. 2A, a device substrate 21 on which organicelectroluminescent elements are arrayed is provided. This devicesubstrate 21 may be a known one in the art, for which there is used, forexample, quartz, glass, a metal foil or a resin sheet or film. Of these,quartz or glass is preferred. With resin films or sheets, there areused, as a resin, methacrylic resins such as polymethyl methacrylate(PMMA), polyesters such as polyethylene terephthalate (PET),polyethylene naphthalate (PEN), polybutylene naphthalate (PBN) and thelike, and polycarbonate resins. These resins should be used in the formof a laminated structure or after surface treatment so as to suppresswater permeability and gas permeability. Alternatively, a TFT substratewherein TFT (thin film transistor) is formed on a support substrate madeof such a material as mentioned above may also be used. It will be notedthat where a display device fabricated herein is of the transmissiontype wherein luminescence is taken out from the device substrate 21side, the device substrate should be made up of a light transmissivematerial.

Next, a lower electrode 23 used, for example, as an anode is formed in apattern on the device substrate 21.

The lower electrode 23 is made of an electrode material whose workfunction from a vacuum level thereof is so great as to efficientlyinject holes. Such a material includes, for example, a metal such asaluminium (Al), chromium (Cr), molybdenum (Mo), tungsten (W), copper(Cu), silver (Ag) or gold (Au), an alloy thereof, or an oxide of themetal or alloy, an alloy of tin oxide (SnO₂) and antimony (Sb), ITO(indium tin oxide), InZnO (indium zinc oxide) and an alloy of zinc oxide(ZnO) and aluminium, or oxides of the metals or alloys. These may beused singly or in admixture.

The lower electrode 23 may be formed as a laminated structure thatincludes a first layer having excellent light reflectivity and a secondlayer formed on the top of the first layer and having opticaltransparency and a great work function.

In this case, the first layer is made of an alloy having aluminium as amain component. The sub-component may be one wherein at least oneelement whose work function is relatively smaller than aluminium used asthe main component is contained. Such a sub-component preferablyincludes a lanthanide element. Although the work function of thelanthanide element is not so great, the stability of the anodecontaining these elements is improved and the hole injection property ofthe anode is satisfied. Aside from the lanthanide element, there may becontained another element, such as silicon (Si) or copper (Cu), as thesub-component.

The content of the sub-component in the aluminium alloy layer serving asthe first layer is preferably in the range of about not larger than 10wt % in total when Nd, Ni and/or Ti for stabilizing aluminium is used,for example. In doing so, while keeping the reflectivity in thealuminium alloy layer, the aluminium alloy layer can be stably heldduring the fabrication process of an organic electroluminescent element,and good processing accuracy and chemical stability are ensured. Inaddition, the lower electrode 23 can be improved in conductivity andadhesion with the substrate 1.

The second layer is, for example, a layer which is made of at least oneof an aluminium alloy oxide, molybdenum oxide, zirconium oxide, chromiumoxide and tantalum oxide. If, for example, an aluminium alloy oxidelayer (including a natural oxide film) containing a lanthanide elementas a sub-component is used as the second layer, the optical transparencyof the second layer becomes good because of the high transparency of theoxide of a lanthanide element. This enables the reflectivity at thesurface of the first layer to be held high. Moreover, the second layermay be a transparent, conductive layer made of ITO (indium tin oxide) orIZO (indium inc oxide). These conductive layers are able to improve anelectron injection characteristic of the lower electrode 23.

The lower electrode 23 may be provided with a conductive layer at a sidecontacting the device substrate 21 so as to improve adhesion between thelower electrode 23 and the device substrate 21. Such a conductive layeris, for example, a transparent conductive layer made of ITO, IZO or thelike.

Where a drive system of a display device arranged by use of the organicelectroluminescent elements is of an active matrix type, the lowerelectrode 23 is provided as patterned for every pixel and connected to adrive thin film transistor provided on the device substrate 21.

Next, after formation of such a lower electrodes 23 (anodes herein) asset out above, an insulating film 25 is formed in pattern to cover theperiphery of individual lower electrodes 23 therewith. This permits anexposed portion of the lower electrode 23 from a window formed in theinsulating film 25 to be provided as a pixel region wherein individualorganic luminescent elements are disposed. This insulating film 25 isconstituted of an organic insulating material such as, for example, apolyimide, a photoresist or the like or an inorganic insulating filmsuch as silicon oxide.

Thereafter, a hole injection layer 27 is formed as a common layer forcovering the lower electrode 23 and the insulating film 25, followed byfurther formation of a hole transport layer 29 serving as a common layerfor covering the hole injection layer 27.

The hole injection layer 27 and the hole transport layer 29 are,respectively, provided so as to enhance a hole injection efficiency tothe luminescent layer. The materials for the hole injection layer 27 orhole transport layer 29 include, for example, benzine, styrylamine,triphenylamine, porphyrin, triphenylene, azatriphenylene,tetracyanoquinodimethane, triazole, imidazole, oxadiazole,polyarylalkane, phenylenediamine, arylamine, oxazole, anthracene,fluorenone, hydrazone, stilbene or derivatives thereof, or polysilanecompounds, vinyl carbazole compounds, thiophene compounds, orheterocyclic conjugated monomers, oligomers or polymers such as anilinecompounds.

More specific materials for the hole injection layer 27 or holetransport layer 29 include α-naphthylphenylphenylenediamine, porphyrin,metal tetraphenylporphyrin, metal naphtalocyanine,hexacyanoazatriphenylene, 7,7,8,8-tratracyanoquinodimethane (TCNQ),7,7,8,8-tetracyano-2,3-5,6-tetrafluoroquinodimethane (F4-TCNQ),tetracyano-4,4,4-tris(3-methylphenylphenylamino)triphenylamine,N,N,N′,N′-tetrakis(p-tolyl)-p-phenylenediamine,N,N,N′,N′-tetraphenyl-4,4′-diaminobiphenyl, N-phenylcarbazole,4-di-p-tolylaminostilbene, poly(paraphenylene vinylene), poly(thiophenevinylene), poly(2,2′-thienylpyrrole) and the like although not limitedthereto.

The hole injection layer 27 ad hole transport layer 29 may be formed asa laminated structure wherein plural layers are laminated, respectively.

The steps set out hereinabove may be carried out in the same manner asordinary steps of fabricating a display device using an organicelectroluminescent element. In a next step, luminescent layers of therespective colors are formed on the thus formed hole transport layers bya thermal transfer process. In this step, the use of the transfersubstrate 1 illustrated with reference to FIG. 1 is a characteristicfeature of this embodiment.

More particularly, as shown in FIG. 2B, the transfer substrate 1 rhaving the red transfer layer 17 r illustrated before is provided. Thistransfer substrate 1 r is disposed in face-to-face relation with thedevice substrate 21 forming the hole transport layer 29 thereon.

The transfer substrate 1 r and the device substrate 21 are so arrangedthat the transfer layer 17 r and the hole transport layer 29 are facingeach other. Moreover, the device substrate 21 and the transfer substrate1 r may be brought into intimate contact with each other so that thehole transport layer 29 which is an uppermost layer at the devicesubstrate 21 side and the transfer layer 17 r which is an uppermostlayer at the transfer substrate 1 r side are contacted with each other.In such a case, the transfer substrate 1 r is left supported on theinsulating film 25 at the device substrate 21 side, and the transfersubstrate 1 r does not contact with a portion of the hole transportlayer 29 on the lower electrode 23.

In this condition, a laser beam by of a wavelength, for example, of 800nm is irradiated from the transfer substrate 1 r side which is inface-to-face relation with the device substrate 21. On this occasion,the laser beam by is spot-irradiated selectively on portionscorresponding to red luminescent element-forming regions.

This permits the laser beam by to be absorbed in the light-heatconversion layer 13 and the transfer layer 17 r is sublimated by use ofthe heat to allow thermal transfer on the device substrate 21 side. Inthis way, a red luminescent layer 17 rr, which is formed by thermallytransferring the transfer layer 17 r on the hole transport layer 29formed on the device substrate 21 in high positional accuracy, is formedin pattern.

In such a thermal transfer, an irradiation energy is set at a relativelyhigh level, so that the luminescent layer 17 rr is formed as a mixedlayer wherein the respective constituent materials of the transfer layer17 r are substantially uniformly mixed together.

It is important here that the laser beam by be irradiated so as tocompletely cover, with the luminescent layer 17 rr, the lower electrode23 at the portion thereof exposed from the insulating film 25 in theluminescent element-forming portion (pixel region).

Next, as shown in FIG. 3A, the transfer substrate 1 g having the greentransfer layer 17 g, which is arranged as stated hereinbefore, isprovided. This transfer substrate 1 g is disposed in face-to-facerelation with the device substrate 21 being formed a hole transportlayer 29 thereon, followed by repeating such a thermal transfer step ofirradiating a laser beam hν as set out above to form a green luminescentlayer 17 gg at a portion corresponding to a green luminescentelement-forming region.

Thereafter, as shown in FIG. 3B, a blue luminescent layer 17 bb isformed at a portion corresponding to a blue luminescent element-formingregion. The formation of the blue luminescent layer 17 bb may be carriedout by a conventional thermal transfer process or by a vacuum depositionprocess.

It will be noted that although the thermal transfer steps repeated inthis way may be carried out under an atmospheric pressure, it ispreferred to carry out the steps in vacuum. When the thermal transfer iscarried out in vacuum, a transfer using a laser of a lower energybecomes possible and an adverse thermal influence on the luminescentlayer being transferred can be mitigated. Moreover, the thermal transferstep carried out in vacuum preferably increases mutual adhesion of thesubstrates, resulting in a good transfer pattern accuracy. In addition,when all the processes are continuously performed in vacuum, it may bepossible to prevent the elements from being degraded.

In the step of the selective spot irradiation of the laser beam hν asset forth above, where the drive portion of a laser head of a laser beamirradiation device is provided with a precise alignment mechanism, thelaser beam hν can be irradiated on the transfer substrate along thelower electrode 23 at an appropriate spot diameter. In this case, it isnot necessary to exactly align the substrate 1 with the transfersubstrate. On the other hand, where the drive portion of a laser head isnot provided with a precise alignment mechanism, it is necessary toform, at the transfer substrate side, a light-shielding film that limitsa region where the laser beam hν is irradiated. More particularly, alight-shielding film that is a high reflection metal layer reflecting alaser beam and provided with an opening is provided at a back surface ofthe transfer substrate 11. A low reflection metal may be formed on thelight-shielding film. In this case, the alignment between the devicesubstrate 2 and the transfer substrate 1 has to be made exactly.

Thereafter, as shown in FIG. 4A, an electron transport layer 31 isformed entirely over the device substrate 21, on which the respectivecolor luminescent layers 17 rr, 17 gg and 17 bb have been formed,according to a vacuum deposition film formation. This electron transportlayer 31 is vacuum deposited and formed as a common layer over theentire surface on the device substrate 21.

This electron transport layer 31 is to transport electrons injected fromthe cathode to the luminescent layers 17 rr, 17 gg and 17 bb. Thematerials for the electron transport layer 31 include, for example,quinoline, perylene, phenanthroline, bisstyryl, pyrazine, triazole,oxazole, oxadiazole, fluorenone, and derivatives or metal complexesthereof. Specific examples include tris(8-hydroxyquinoline)aluminium(abbreviated as Alq3), anthracene, naphthalene, phenanthrene, pyrene,perylene, butadiene, coumarin, acridine, stilbene, 1,10-phenanthroline,or derivatives and metal complexes thereof.

An organic layer 33 is constituted of the thus formed hole injectionlayer 27, hole transport layer 29, individual color luminescent layers17 rr, 17 gg 17 bb and electron transport layer 31.

Next, as shown in FIG. 4B, an upper electrode (cathode herein) 35 isformed on the organic layer 33. The upper electrode 35 used as a cathodeis constituted, for example, of a double-layered structure wherein afirst layer and a second layer as viewed from the organic layer 33 sideare laminated.

The first layer is made of a material that has a small work function andgood light transmittivity. Examples of the material include lithiumoxide (Li₂O) that is an oxide of lithium (Li), cesium carbonate (Cs₂CO₂)that is a composite oxide of cesium (Cs), and a mixture of the oxide andthe composite oxide. The first layer 15 a is not limited to thematerials mentioned above and may be made, for example, of an alkalineearth metal such as calcium (Ca), barium (Ba) or the like, an alkalimetal such as lithium, cesium or the like, or a metal whose workfunction is small, such as indium (In), magnesium (Mg) or the like.Moreover, oxides, composite oxides and fluorides of these metals may beused singly, or mixtures or alloys of the metals, and oxides, compositeoxides and fluoride thereof may also be used so as to enhance stabilitythereof.

The second layer is made of a material having optical transparency, suchas MgAg or the like, in the form of a thin film. This second layer 15 bmay also be in the form of a mixed layer containing an organicluminescent material such as an aluminium quinoline complex, astyrylamine derivative, a phthalocyanine derivative or the like. In thiscase, a layer having optical transparency and made, for example, of MgAgmay be separately provided as a third layer.

Where a display device made herein is of an active matrix type, such anupper electrode 35 as set out above is formed as a blanket film over thedevice substrate 21 in such a state as to be insulated from the lowerelectrode 23 by means of the organic layer 33 and the insulating film 25and is used as a common electrode of the individual pixels.

Individual organic electroluminescent elements, i.e. the red luminescentelement 37 r, green luminescent element 37 g and blue luminescentelement 37 b, are formed at the respective portions where the organiclayer 33 including the respective color luminescent layers 17 rr, 17 ggand 17 bb is sandwiched in the laminated structure of the lowerelectrode 23 and the upper electrode 35.

It will be noted that the upper electrode 35 is not limited to alaminated structure of such a type as set out above, but an optimumcombination or a laminated structure, which depends on the type ofdevice fabricated, may be taken. For instance, the arrangement of theupper electrode 35 of the above embodiment is directed to a laminatedstructure wherein the functions of the respective layers of theelectrode are separated from each other, i.e. an inorganic layer (firstlayer) facilitating injection of electrons into the organic layer 33 andan inorganic layer (second layer) serving as an electrode are separatedfrom each other. However, the inorganic layer facilitating the electroninjection into the organic layer 33 may be one that also serves as anelectrode, and these layers may be formed as a single layer structure.Additionally, a transparent electrode such as ITO may be formed on thissingle layer structure to provide a laminated structure.

Although the electric current applied to the respective colorluminescent elements 37 r, 37 g and 37 b arranged in such a way as setout hereinbefore is usually a direct current, a pulse current or analternating current may also be used. Although no limitation is placedon the current value or voltage value so far as they are used withinranges where the elements are not broken down, it is preferred thatluminescence is generated efficiently by use of an electric energy beingas small as possible when taking the consumption power and life of theorganic electroluminescent element into consideration.

Where these organic electroluminescent elements 37 r, 37 g and 37 b haveeach a cavity structure, the upper electrode 35 is constituted of asemi-transparent semi-reflective material. Luminescent light havingbeing subjected to multiple interference between the light reflectionsurface at the lower electrode 23 side and the light reflection surfaceat the upper electrode 35 side is taken out from the upper electrode 35side. In this case, the optical distance between the light reflectionsurface at the lower electrode 23 side and the light reflection surfaceat the upper electrode 35 side is defined by means of a wavelength oflight to be taken out, and the thicknesses of the respective layers areso set as to satisfy the optical distance. In the organicelectroluminescent element of such an upper surface luminescence type asset out above, when the cavity structure is positively used, animprovement in luminescence extraction efficiency to outside and controlof luminescent spectra can be possible.

Furthermore, although not shown in the figures, it is preferred that theorganic electroluminescent elements 37 r, 37 g and 37 b are,respectively, used by coverage with a protective layer (passivationlayer) so as to prevent the organic materials from degradation withmoisture, oxygen and the like in air. For the protective film, there isused a silicon nitride (typically of which is Si₃N₄), a silicon oxide(typically of which is SiO₂) film, a silicon nitride-oxide (SiN_(x)O_(y)with a compositional ratio of X>Y) film, a silicon oxide-nitride(SiO_(x)N_(y) with a compositional ratio X>Y) film, a thin film mainlycomposed of carbon such as DLC (diamond like carbon, a CN (carbonnanotube) film, or the like. These films are preferably formed insingle-layered or multi-layered structure. The protective film made of anitride is dense in nature and is thus preferably used because of itsvery high blocking effect on moisture, oxygen and other impuritiesadversely influencing the organic electroluminescent elements 37 r, 37 gand 37 b.

It will be noted that in the above embodiment, the invention isdescribed in detail by using the case where the organicelectroluminescent elements are of the upper surface luminescence type.However, the organic electroluminescent elements of the presentinvention are not limited to application to such an upper surfaceluminescence type as mentioned above, but may be widely applicable tosuch an arrangement wherein an organic layer having at least luminescentlayer is held between the anode and the cathode. Accordingly, if acathode, an organic layer and an anode are successively laminated in theorder from a substrate side or if an electrode located at the same sideas a substrate (i.e. a lower electrode for use as a cathode or anode) isconstituted of a transparent material and an electrode located at a sideopposite to the substrate (i.e. an upper electrode used as a cathode oranode) is constituted of a reflective material, the present invention isapplicable to an organic electroluminescent element of a bottom surfaceluminescence type (so-called transmission type) which emits light onlyfrom the bottom electrode side.

The organic electroluminescent element fabricated herein may be onewhich is formed by sandwiching an organic layer between a pair ofelectrodes (anode and cathode). In this sense, the present invention isnot limited to the arrangement including only a pair of electrodes andan organic layer, but other constituent elements or layers (e.g. aninorganic compound layer and an inorganic component) may benon-exclusively used within ranges not impeding the effect of thepresent invention.

It will be noted that the display device using the organicelectroluminescent elements fabricated herein is not limited to onewhich is sectionally shown in FIG. 4B. For instance, a display device 41having such an arrangement as shown in FIG. 5 may be used. It is to benoted that like members or elements as in the display device of FIG. 4Bare designated by like reference numerals in FIG. 5.

More particularly, like a display device 41 as shown in FIG. 5, a holeinjection layer 27 and a hole transport layer 29 may be patterned forevery element. It is important to note that the red luminescent layer 17rr and the green luminescent layer 17 gg formed on the hole transportlayer 29 be, respectively, formed using a similar transfer substrate asillustrated with reference to FIGS. 2A to 3B. Moreover, the blueluminescent layer 17 bb is formed by such a transfer process as set outabove or by a vacuum deposition process.

The electron transport layers 31 of these luminescent layers 17 rr, 17gg and 17 bb may be patterned for every element.

The respective layers including the lower electrode layer 23 to theupper electrode 35 other than the luminescent layers 17 rr, 17 gg, 17 bbillustrated hereinabove can be formed by a dry process such as a vacuumdeposition process, an ion beam process (EB process), a molecular beamepitaxy process (MBE process), a puttering process, an organic vaporphase deposition (OVPD) process or the like.

The organic layers other than the luminescent layers 17 rr, 17 gg and 17bb may be formed by processes including, aside from the above-indicatedprocesses, wet processes including coating processes such as a lasertransfer process, a spin coating process, a dipping process, a doctorblade process, a jet coating process, a spray coating process and thelike, and printing processes such as an ink jet process, an offsetprocess, a letterpress process, an intaglio printing process, a screenprinting process, a microgravure coating process and the like. Dependingon the properties of the respective organic layers and members, the dryand wet processes may be used in combination.

It will be noted that as shown in FIG. 5, the respective portions of theorganic layer formed as a pattern for every organic electroluminescentelements 37 r, 37 g or 37 b may be formed, for example, by a vacuumdeposition process or transfer process using a mask.

According to the transfer substrate 1 and the method of fabricating anorganic electroluminescent element using the transfer substrate of theembodiments illustrated hereinbefore, the transfer layers 17 r and 17 gof the transfer substrates 1 r and 1 g are, respectively, formed of aternary material or composition of a) metal complex, b) fluorescentluminescent dopant and c) aromatic hydrocarbon whose matrix skeleton hasfour to seven rings, so that the luminescent layers 17 rr, 17 gg formedby sublimation of the transfer layer 17 are also constituted of theternary material. It has been confirmed that in the luminescent layers17 rr, 17 gg composed of such a ternary material, although the aromatichydrocarbon does not contribute to luminescence, a higher luminescentefficiency and a longer half-time luminance life are attained whencompared with the case where no aromatic hydrocarbon is present.Moreover, the resulting luminescent layer is such that the three typesof materials are more uniformly mixed and the hν material ratios aremore accurately controlled than that formed by vacuum co-deposition.

Eventually, the luminescent layers 17 rr, 17 gg made of the ternarymaterial capable of achieving a high luminance efficiency and animproved half-time luminance life can be formed more uniformly at moreprecise ratios. This makes it possible to obtain the organicelectroluminescent elements 37 r, 37 g whose luminescence efficiency andhalf-time luminescence life are further improved.

Since the organic electroluminescent elements 37 r, 37 g having a highluminescence efficiency are used, the luminance life of the displaydevice 41 can be improved and an effect of reducing consumption power isbrought about. Accordingly, the elements can be favorably employed as aflat panel display or a flat luminescent body such as a wall-hungtelevision and are also applicable to as a light source such as forduplicating machines and printers, a light source such as for liquidcrystal displays, a display plate, a marker lamp and the like.

In the foregoing instances, embodiments wherein the present invention isapplied to a display device of an active matrix type have beenillustrated. As a matter of course, the display device of the presentinvention may be applicable to a passive matrix type with similarresults being obtained.

<Schematic Arrangement of Display Device>

FIGS. 6A and 6B are a view showing an example of a display panel appliedto a display device of the foregoing embodiments wherein FIG. 6A is aschematic view of the display panel and FIG. 6B is a pixel circuitdiagram therefor. In these figures, there is shown a display panel of adisplay device 41 of an active matrix type using the organicelectroluminescent elements 37 r, 37 g and 37 b as a luminescentelement.

As shown in FIG. 6A, a display region 21 a and a peripheral region 21 bare set on a device substrate 21 of the display device 41. The displayregion 21 a has a plurality of scanning lines 43 and a plurality ofsignal lines 45 arranged in a matrix with one pixel A being provided atindividual intersections to provide a pixel array unit as a whole. Oneof the organic electroluminescent elements 37 r, 37 g and 37 b isprovided at each of these pixels A. The peripheral region 21 b isprovided thereon with a scanning line drive circuit B for scan drivingthe scanning line 43 and a signal line drive circuit C for feeding avideo signal (i.e. an input signal) corresponding to luminanceinformation to the signal line 45.

As shown in FIG. 6B, a pixel circuit provided for every pixel A isconstituted, for example, of one of the organic electroluminescentelements 37 r, 37 g and 37 b, a drive transistor Tr1, a write transistor(sampling transistor) Tr2, and a storage capacitor Cs. When the scanningline drive circuit B drives the scanning line 43, the video signalsupplied from the signal line 45 through the write transistor Tr2 isretained in the storage capacitor Cs. A current corresponding to anamount of stored signal is fed to the respective organicelectroluminescent elements 37 r, 37 g and 37 b, and the organicelectroluminescent elements 37 r, 37 g and 37 b emit luminescence at aluminance corresponding to the current value.

It will be noted that the arrangement of the pixel circuit illustratedabove is shown only by way of example, and a capacitor element may beprovided within the pixel circuit, if necessary, or a plurality oftransistors may be provided to constitute a pixel circuit. Moreover, theperipheral region 21 b should be additionally provided with a necessarydrive circuit depending on the alteration of the pixel circuit.

Such an arrangement of the display device 41 as set out aboveencompasses a sealed module shape as is particularly shown in FIG. 7.For instance, a sealing portion 51 is provided so as to surround thedisplay region 21 a serving as a pixel array unit, and this sealingportion 51 used as a bonding agent is bonded to an opposite unit (sealsubstrate 52) such as of transparent glass or the like, therebyproviding a display module. This transparent seal substrate 52 may beprovided with a color filter, a protective film, a light-shielding filmand the like. It is to be noted that the device substrate 21 used as adisplay module forming the display region 21 a thereon may be providedwith a flexible printed board substrate 53 for permitting signals to beinputted from outside to the display area 21 a or to be outputted fromthe display area 21 a to outside.

Application Examples

The display device according to the above embodiment of the presentinvention is applicable as display devices to various types ofelectronic devices in all fields. The electronic devices displayingvideo signals inputted thereto or video signals produced therein asimages or pictures, includes, for example, mobile terminal devices suchas a notebook-sized personal computer, a cell phone and the like, adigital camera, a video camera, and the like display devices, as shownin FIGS. 8 to 12. Examples of the electronic devices to which thepresent invention is applicable are illustrated.

FIG. 8 is a perspective view showing a television set to which thepresent invention is applied. The television of this application exampleincludes a display screen unit 101 made up of a front panel 102, afilter glass 103 and the like wherein the display device of theinvention is used as the display screen unit 101.

FIGS. 9A and 9B are, respectively, a schematic view showing a digitalcamera to which the invention is applied, wherein FIG. 9A is aperspective view as viewed from a front side and FIG. 9B is aperspective view as viewed from a back side. The digital camera of thisapplication example includes a flash light emission unit 111, a displayunit 112, a menu switch 113, a shutter button 114 and the like whereinthe display device of the present invention is used as the display unit12.

FIG. 10 is a perspective view showing a notebook-sized personal computerto which the present invention is applied. The notebook-sized personalcomputer of this application example includes a body 121, a keyboard 122used when inputting letters and the like, a display unit 123 displayingimages and the like, wherein the display device of the present inventionis used as the display unit 123.

FIG. 11 is a perspective view showing a video camera to which theinvention is applied. The video camera of this application exampleincludes a body 131, an objective lens 132 provided at a forwardlyfacing side, a shooting start/stop switch 133, a display unit 134 andthe like, wherein the display device of the invention is used as thedisplay unit 134.

FIGS. 12A to 12G are, respectively, a schematic view showing a portableterminal device, e.g. a cell phone to which the present invention isapplied, wherein FIG. 12A is a front view showing the cell phone in anopened state, FIG. 12B is a side view thereof, FIG. 12C is a front viewshowing the cell phone in a closed state, FIG. 12D is a left side view,FIG. 12E is a right side view, FIG. 12F is a top view and FIG. 12G is abottom view. The cell phone of this application example includes anupper casing 141, a lower casing 142, a connection (a hinge herein) 143,a display 144, a sub-display 145, a picture light 146, a camera 147 andthe like. The portable terminal device is fabricated by using thedisplay device to which the present invention is applied as the display144 or the sub-display 145.

The fabricating procedures of organic electroluminescent elements ofexamples of the invention and comparative examples are described withreference to FIGS. 1 to 3B along with the results of evaluation thereof.

Example 1

An organic electroluminescent element for a green light is fabricated asfollows.

(1) Initially, a device substrate 21 made of a 30 mm×30 mm glass sheetwas provided, on which a lower electrode (anode) 23 made of a190-nm-thick Ag alloy (reflective layer) and a 12.5-nm-thick ITOtransparent electrode laminated thereon was formed to make a cell for anorganic electroluminescent element for upper surface luminescence. Next,a silicon oxide insulating film 25 was formed in a thickness of about 2μm by a sputtering process so as to cover the periphery of the lowerelectrode 23 therewith, followed by exposing the lower electrode 23 by alithographic method to provide a pixel region.

Next, according to a vacuum deposition process, a film of m-MTDATA ofthe following formula was formed as a hole injection layer 27 of anorganic layer in a thickness of 12 nm (at a deposition rate of 0.2 to0.4 nm/second). M-MTDATA means4,4′,4″-tris(phenyl-m-tolylamino)triphenylamine.

Thereafter, a film made of the following α-NPD was formed as a holetransport layer 29 in a thickness of 6 nm (at a deposition rate of 0.2to 0.4 nm/second). The α-NPD meansN,N′-bis(1-naphthyl)-N,N′-diphenyl[1,1′-biphenyl]-4,4′-diamine.

(2) On the other hand, a transfer substrate 1 g for forming a greenluminescent layer thereon was made in the following way. Initially, a200-nm-thick light-heat conversion layer 13 made of molybdenum wasformed on a glass support substrate 21 according to an ordinarysputtering method. Next, a 100-nm-thick oxidation protective layer 15made of silicon nitride SiN_(x) was formed on the light-heat conversionlayer 13 by a CVD process.

A 25-nm-thick transfer layer 17 g was vacuum deposited on the oxidationprotective layer 15. The transfer layer 17 g was formed by ternarydeposition of a) the following 8≡hydroxyquinoline aluminium (Alq3) as ametal complex, b) the following green fluorescent luminescent materialof10-(2-benzothiazolyl)-1,1,7,7-tetraethyl-2,3,6,7-tetrahydro-1H,5H,11H-benzo[I]pyrano[6,7,8-ij]quinolizin-11-one(C-545T: a commercial name of Aldrich Corporation) as a fluorescentluminescent dopant, and c) the following diebenzo[b,k]perylene as anaromatic hydrocarbon at relative thickness ratios of 79.5%, 0.5% and20%, respectively.

(3) Next, the device substrate 21 and the transfer substrate 1 g wereplaced in face-to-face relation with each other so that the holetransport layer 29 and the transfer layer 17 g were facing each other,and were brought into intimate contact in vacuum. Both substrates had aspace of about 2 μm kept over the lower electrode 23 ascribed to thethickness of the insulating film 25. In this condition, a laser beamwith a wavelength of 800 nm was irradiated from the back side of thetransfer substrate 1 g at a position opposing to the pixel region of thedevice substrate 21 to thermally transfer the transfer layer 17 g fromthe transfer substrate 1 g to the device substrate 21 side bysublimation, thereby forming a green luminescent layer 17 gg. The spotsize of the laser beam was set at 300 μm×10 μm. The laser beam wasscanned in a direction intersecting with the length of the beam. Theenergy density was at 2.6 E⁻³ mj/μm².

(4) The device substrate 21 on which the luminescent layer 17 gg hadbeen formed by the transfer was heated at 100° C. for 30 minutes in anatmosphere of nitrogen used as an inert gas.

(5) After the heating, a blue luminescent layer obtained by mixing9,10-di(2-naphthyl)anthracene (AND) of the following formula used as ahost material and a styrylamine derivative of the following formula usedas a blue luminescent guest material at a relative thickness ratio of2.5% was laminated on the top of the luminescent layer 17 gg by vacuumdeposition. This blue luminescent layer is one which is formed as acommon layer for individual pixels after formation of a red luminescentlayer and a green luminescent layer as individual pixels by a transferprocess when fabricating a full color display device and which does notinfluence luminescence of the green and red pixels.

(6) Next, 8≡hydroxyquinoline aluminium (Alq3) was vacuum deposited in athickness of about 20 nm as an electron transport layer 31.Subsequently, LiF was vacuum deposited in a thickness of about 0.3 nm(at a deposition rate of up 0.01 nm/second) as an electron injectionlayer (or a first layer of an upper electrode). Thereafter, MgAg wasvacuum deposited in a thickness of 10 nm as a cathode serving as anupper electrode 35 thereby obtaining a green luminescent element 37 g.

Examples 2 and 3 and Comparative Examples 1, 2 and 3

Example 1 was repeated except that materials indicated in the followingTable 1 were used as a material for the transfer layer 17 g in theprocedure of making the transfer substrate 1 g in (2) of Example 1,thereby obtaining a green luminescent element 37 g. It will be notedthat in Comparative Example 3, 9,10-diphenylaminoanthracene was used inplace of a) the metal complex used as a host material in Example 1.

TABLE 1 Transfer layer 17g a) Metal b) Fluorescent c) Aromatic LuminanceLife complex luminescent dopant hydrocarbon efficiency (T90) (content)(content) (content) (cd/A) (Hr) Example 1 Alq3 C-545T Dibenzo[b,k] 13120 (79.5%) (0.5%) perylene (20.0%) Example 2 Gaq3 C-545T Dibenzo[b,k]13 120 (79.5%) (0.5%) perylene (20.0%) Example 3 Alq3 9,10- Dibenzo[b,k]15 100 (65.0%) Diphenylaminoanthracene perylene (5.0%) (30.0%)Comparative Alq3 C-545T 12 20 Example 1 (99.5%) (0.5%) Comparative Alq39,10- — 13 25 Example 2 (95.0%) Diphenylaminoanthracene (5.0%)Comparative ADN 9,10- Dibenzo[b,k] 14 32 Example 3 (75.0%)Diphenylaminoanthracene perylene (5.0%) (20.0%)

<Results of Evaluation-1>

The organic electroluminescent elements of Examples 1 to 3 andComparative Examples 1 to 3 made in the way stated above were subjectedto measurements of a luminance efficiency by driving at a currentdensity of 10 mA/cm² and a time, as a life (T90), before a luminanceobtained by application of a current density of 100 mA/cm² was reducedto 90%. The results are also shown in Table 1.

From these results of the measurements, it has been confirmed that theorganic electroluminescent elements of Examples 1 to 3 wherein therespective transfer layers 17 g are formed as containingdibenzo[b,k]perylene as c) an aromatic hydrocarbon along with a) metalcomplexes used as a host material and b) fluorescent luminescent dopantsare remarkably improved in luminance life while keeping a luminanceefficiency when compared with the organic electroluminescent elements ofComparative Example 1 and 2 wherein the transfer layer is free of c)aromatic hydrocarbon. The comparison between Examples 1 and 2 andComparative Example 1, and also between Example 3 and ComparativeExample 2 reveals that the luminance life is remarkably improved withoutdepending on the green b) fluorescent luminescent dopant contained.

In Comparative Example 3, 9,10-diphenylaminoanthracene was used in placeof a) the metal complex used as a host material in Example 1. In thiscase, although the luminous efficiency is kept, the life is poorer thanthose of Examples 1 to 3.

Example 4

Example 1 was repeated except that the transfer layer 17 g was formed asa double-layered structure in the procedure of making the transfersubstrate 1 g in (2) of Example 1, thereby obtaining a green luminescentelement 37 g. For the formation of the transfer layer 17 g, a) a metalcomplex (Alq3) and b) a fluorescent luminescent dopant (C-545T) werevacuum co-deposited at a relative thickness ratio of 99.5%:0.5%. Next,c) an aromatic hydrocarbon (dibenzo[b,k]perylene) was vacuum depositedin a thickness of 5 nm to provide a double-layered structure.

The resulting organic electroluminescent element exhibited a luminousefficiency of 7.5 cd/A by driving at a current density of 10 mA/cm² anda life (T90) of 110 hours when driven at a current density of 100mA/cm². When compared with the results of evaluation in Example 1, ithas been confirmed that in the case where the transfer layer 17 g isformed as a double-layered structure using the three types of materialsa), b) and c) as the transfer layer 17 g of the transfer substrate 1 g,the resulting organic electroluminescent element using the transferlayer 17 g is remarkably improved in luminance life over ComparativeExamples 1 and 2

Example 5

Example 1 was repeated except that the transfer layer 17 g was formed asa three-layered structure in the procedure of making the transfersubstrate 1 g in (2) of Example 1, thereby obtaining a green luminescentelement 37 g. The transfer layer 17 g was formed by initially vacuumdepositing a) a metal complex (Alq3) in a thickness of 14 nm,subsequently b) a fluorescent luminescent dopant(9,10-diphenylaminoanthracene) in a thickness of 1 nm and finally c) anaromatic hydrocarbon (dibenzo[b,k]perylene) in a thickness of 5 nm toprovide a three-layered structure.

The resulting organic electroluminescent element had a luminanceefficiency of 7.5 cd/A when driven at a current density of 10 mA/cm² anda life (T90) of 110 hours when driven at a current density of 100mA/cm². The comparison with the results of evaluation in Example 1reveals that in the case where the transfer layer 17 g is formed as athree-layered structure using the three types of materials a), b) and c)as the transfer layer 17 g of the transfer substrate 1 g, the resultingorganic electroluminescent element using the transfer layer 17 g is muchremarkably improved in luminance life over Comparative Examples 1 and 2.

Examples 6 and 7 and Comparative Example 4

Organic electroluminescent elements of red luminescence were made in thefollowing way.

The general procedure of Example 1 was repeated except that thematerials for forming the transfer layer 17 g in the same manner as forthe transfer substrate 1 g in (2) of Example 1 were changed to materialsfor forming a transfer layer 17 r that was used to form a redluminescent layer as indicated in Table 2, thereby obtaining a redluminescent element 37 r.

In this regard, however, an oxidation protective layer 15 made ofsilicon nitride SiN_(x) was formed in a thickness of 120 nm and thetransfer layer 17 r was formed in a thickness of 40 nm.

TABLE 2 Transfer layer 17r b) Fluorescent a) Metal luminescent c)Aromatic Luminous Life complex dopant hydrocarbon efficiency (T90)(content) (content) (content) (cd/A) (hours) Example 6 Alq3 BSN3,10-Bis(2- 6.1 90 (40.0%) (10.0%) naphthylperylene) (50.0%) Example 7Alq3 5,6,11,12- 8.3 130 (40.0%) tetraphenyltetracene (50.0%) ComparativeAlq3 — 5.7 20 Example 4 (90.0%)

<Results of Evaluation-2>

The thus fabricated organic electroluminescent elements of Examples 6and 7 and Comparative Example 4 were subjected to measurements of aluminous efficiency by driving at a current density of 10 mA/cm² and atime, as a life (T90), before a luminance obtained by application of acurrent density of 70 mA/cm² was reduced to 90%. The results are alsoshown in Table 2 above.

From these results of the measurements, it has been confirmed that theorganic electroluminescent elements of Examples 6 and 7 made ascontaining in the transfer layer 17 r c) the aromatic hydrocarbon alongwith a) the metal complexes as a host material and b) the fluorescentluminescent dopant are improved in the luminous efficiency andremarkably improved in the luminous life over the organicelectroluminescent element of Comparative Example 4 wherein the transferlayer is free of c) aromatic hydrocarbon. In addition, it will beapparent from Examples 6 and 7 that the luminance life is remarkablyimproved without depending on b) the red fluorescent luminescent dopantcontained.

Example 8

Example 6 was repeated except that the transfer layer 17 r was formed asa double-layered structure in the procedure of making the transfersubstrate 1 r in (2) of Example 6, thereby obtaining a red luminescentelement 37 r. More particularly, the transfer layer 17 r was formed byvacuum co-depositing a) metal complex (Alq3) and b) fluorescentluminescent dopant (BSN) at a relative thickness ratio of 80.0%:20.0% ina thickness of 20 nm. Next, c) aromatic hydrocarbon(3,10-bis(2-naphthyl)perylene) was vacuum deposited in a thickness of 20nm to provide a double-layered structure.

The resulting organic electroluminescent element had a luminousefficiency of 6.0 cd/A when driven at a current density of 10 mA/cm² anda life (T90) of 95 hours when driven at a current density of 70 mA/cm².The comparison with the results of evaluation in Example 6 reveals thatin the case where the transfer layer 17 r is formed as a double-layeredstructure using the three types of materials a), b) and c) as thetransfer layer 17 r of the transfer substrate 1 r, the resulting organicelectroluminescent element using the transfer layer 17 r is moreremarkably improved in luminance life over Comparative Example 4.

Example 9

Example 7 was repeated except that the transfer layer 17 r was formed asa three-layered structure in the procedure of making the transfersubstrate 1 r in (2) of Example 7, thereby obtaining a red luminescentelement 37 r. The transfer 17 r was formed by initially vacuumdepositing a) metal complex (Alq3) in a thickness of 16 nm, subsequentlyb) fluorescent luminescent dopant (BSN) in a thickness of 4 nm, andfinally c) aromatic hydrocarbon (5,6,11,12-tetraphenyltetracene) in athickness of 20 nm to provide a three-layered structure.

The resulting organic electroluminescent element had a luminousefficiency of 8.5 cd/A when driven at a current density of 10 mA/cm² anda life (T90) of 125 hours when driven at a current density of 70 mA/cm².The comparison with the results of evaluation of Example 4 demonstratesthat that in the case where the transfer layer 17 r is formed as athree-layered structure using the three types of materials a), b) and c)as the transfer layer 17 r of the transfer substrate 1 r, the resultingorganic electroluminescent element using the transfer layer 17 r is moreremarkably improved in luminance life over Comparative Example 4.

Examples 10 and 11

The organic electroluminescent elements of red luminescence were made inthe following way.

The materials for forming the transfer layer 17 g in the procedure ofmaking the transfer substrate 1 g in (2) of Example 1 were changed tomaterials for forming a transfer layer 17 r for forming a redluminescent layer indicated in Table 3 below. Except for this, Example 1was repeated thereby obtaining a red luminescent element 37 r.

It will be noted that an oxidation protective layer 15 made of siliconnitride SiN_(x) had a thickness of 150 nm and the transfer layer 17 rhad a thickness of 40 nm.

TABLE 3 Transfer layer 17r b)Fluorescent a)Metal luminescent c)AromaticLuminous Life complex dopant hydrocarbon efficiency (T90) (content)(content) (content) (cd/A) (hours) Example Gaq3 Compound3,10-Bis(2-naph- 4.5 210 10 (69.0%) (4)-2 thylperylene) (DCJTB) (30.0%) (1.0%) Example Gaq3 Compound 5,6,11,12-Tetra- 7.5 330 11 (40.0%) (3)-21phenylphenyl (10.0%) tetracene (50.0%) b)Fluorescent luminescent dopantsused are, respectively, a pyrane derivative of the following compound(4)-2, i.e.[4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl-4H-pyrane(DCJTB)) and a pyromethene complex of the following compound (3)-21which are illustrated in the foregoing embodiment.

<Results of Evaluation-3>

The thus fabricated organic electroluminescent elements of Examples 10and 11 were subjected to measurements of a luminous efficiency bydriving at a current density of 10 mA/cm² and a time, as a life (T90),before a luminance obtained by application of a current density of 70mA/cm² was reduced to 90%. The results are also shown in Table 3 above.

From these results of the measurements, it has been confirmed that theorganic electroluminescent elements of Examples 10 and 11 made ascontaining in the transfer layer 17 r c) the aromatic hydrocarbon alongwith b) the metal complexes as a host material and b) the fluorescentluminescent dopant are remarkably improved in the luminous life, withoutdepending on the red b) fluorescent luminescent dopants, over theorganic electroluminescent element of Comparative Example 4, as shown inTable 2, using the transfer layer that is free of c) aromatichydrocarbon.

While preferred embodiments of the present invention have been describedusing specific terms, such description is for illustrative purpose only,and it is to be understood that changes and variations may be madewithout departing from the spirit or scope of the following claims.

1. A transfer substrate comprising: a light transmissive supportsubstrate; a light-heat conversion layer on said light transmissivesupport substrate; and a transfer layer on said light heat conversionlayer, wherein, said transfer layer is a layer transferred as aluminescent layer of an organic electroluminescent element and is madeof a metal complex, a fluorescent luminescent dopant and an aromatichydrocarbon whose matrix skeleton has four to seven rings.
 2. Thetransfer substrate according to claim 1, wherein said metal complex is acomplex in which quinolinol is coordinated to a metal selected fromaluminium, gallium and indium.
 3. The transfer substrate according toclaim 1, wherein said aromatic hydrocarbon is used in an amount within arange of not larger than 50 wt % in said transfer layer.
 4. The transfersubstrate according to claim 1, wherein said transfer layer has alaminated structure including a mixed layer of said metal complex andsaid fluorescent luminescent dopant and a layer of said aromatichydrocarbon.
 5. The transfer substrate according to claim 1, whereinsaid transfer layer has a laminated structure including a layer made ofsaid metal complex, a layer of said fluorescent luminescent dopant, anda layer made of said aromatic hydrocarbon.
 6. The transfer substrateaccording to claim 1, wherein said fluorescent luminescent dopant ismade of a green luminescent material or a red luminescent material.
 7. Amethod for fabricating an organic electroluminescent element comprisingthe steps of: forming a pattern of a lower electrode on a devicesubstrate; forming an organic layer including at least a luminescentlayer on said lower electrode; and forming an upper electrode laminatedon said lower electrode through said organic layer, wherein, saidluminescent layer is formed by (a) providing a transfer substrateobtained by forming, on a light transmissive support substrate, a lightheat conversion layer and a transfer layer constituted of three types oforganic materials including a host material and a fluorescentluminescent dopant in this order, (b) placing said transfer substrate inface-to-face relation with said device substrate in such way that saidtransfer layer is opposed to a side of said device substrate, and (c)sublimating said transfer layer by beam irradiation from a side of saidsupport substrate to transfer said transfer layer to above of saiddevice substrate.